Seoul: China will step up inspections along its border with North Korea during the Olympics to try to reduce the growing number of North Korean migrants, an official with South Korea's spy agency said on Tuesday.

The National Intelligence Service official dismissed a news report that China plans to close all bridges into its communist ally during the Olympics and that China has demanded that North Koreans already working in China leave.

An NIS official, citing an internal policy, told The Associated Press that China had no plans to close all bridge links with North Korea "out of concerns of diplomatic friction with North Korea."

The official also said China would not ask all North Koreans in China to leave, saying that Beijing plans to crack down on North Koreans who illegally stay in China and Beijing plans to restrict renewing visas for North Koreans.

A growing number of North Koreans cross into China in search of food and to avoid political oppression and many seek eventual asylum in South Korea.

Activists claim tens of thousands of North Koreans live in hiding in China, where they face forced repatriation to their impoverished homeland if caught.